System and method for attaching stainless steel side plates to the copper/brass tubes of a heat exchanger core

ABSTRACT

A system and method for attaching very thin stainless steel plates to a radiator or heat exchanger core using the CuproBraze® brazing technique. The use of thin stainless steel side plates produces the structural strength needed in the radiator or heat exchanger core assembly without adding an excessive amount of weight. Heretofore, the CuproBraze® brazing technique has not been used with stainless steel. The stainless steel radiator or heat exchanger core side plates need only be about half as thick as a copper/brass side plate to provide the strength needed for support of the radiator or heat exchanger core.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Application No. 61/351,727, filed on Jun. 4, 2010.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH AND DEVELOPMENT

The invention described in this patent application was not the subjectof federally sponsored research or development.

FIELD

The present invention pertains generally to a process of increasing themounting strength of heat exchanger cores using the CuproBraze® brazingtechnique by mounting stainless steel side plates to the core. Thepresent invention more particularly pertains to increasing thestructural strength of radiator or heat exchanger cores by mountingstainless steel side plates to the radiator or heat exchanger core usingthe CuproBraze® soldering technique in a way in which the Cuprobraze®soldering technique has not previously been used.

BACKGROUND

Radiator and heat exchanger cores are made from copper and brass becausecopper and brass possess the ability to transfer more heat per core sizethan any other materials. The thermal efficiency of cores made fromcopper and brass results in smaller sized cores that remove the thermalenergy from the cooling fluid that is typically used to control theoperating temperature of large engines or other heat producers. Copperand brass heat exchangers can operate at temperatures well above 250° C.whereas cores made from other materials such as aluminum are severelycompromised where the cooling fluid temperature passing through the coreis at above 200° C. Therefore, cores made from copper and brass arefound in most radiators and heat exchanger assemblies.

The International Copper Association has specifically developed abrazing/soldering process for the manufacture of heavy-duty mobile andindustrial copper and brass radiators and heat exchangers. This processis commonly known by those skilled in the art by its trademarked name,CuproBraze®. However, if conventional copper and brass materials areused to provide a structure for a radiator or heat exchanger made usingthe CuproBraze® brazing technique to then obtaining the requiredstructural support for the heat exchanger core an requires that anexcessive amount of weight be added to the radiator or heat exchangercore to provide the needed structural support. Added weight isparticularly objectionable if the radiator is used on a racing vehicleas race vehicle builders are continually looking for ways to reduce theweight of a racing vehicle. In addition, added weight significantly addsto the cost of radiator or heat exchanger core assemblies manufacturedusing the CuproBraze® soldering technique.

Accordingly, a need remains in the art for a process of attaching asupport structure to a radiator or heat exchanger core made using theCuproBraze® soldering technique, which support structure provides therequired structural strength and can be attached to the radiator or heatexchanger core using the CuproBraze® soldering technique.

SUMMARY

The system and method of the present invention describes the steps forattaching thin stainless steel plates to the heat exchanger core usingthe CuproBraze® soldering technique and the radiator or heat exchangercore assembly made when the disclosed steps are followed.

The use of thin stainless steel side plates produces the structuralstrength needed for a core used in a radiator or heat exchanger withoutadding an excessive amount of weight. Heretofore, the CuproBraze®soldering technique has not been used with stainless steel. Thereduction in weight of a radiator or heat exchanger core assemblymanufactured by the disclosed system and method occurs because stainlesssteel radiator side plates need only be about half as thick as acopper/brass side plate would need to be to provide the strength neededfor support of the core portion of the radiator or heat exchangerassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the of the present invention may be had byreference to the drawing figures wherein:

FIG. 1 is a simplified view of a radiator or heat exchanger core showingthe position of the stainless steel plates in relation to other elementsof the radiator or heat exchanger core;

FIG. 2 is a simplified view of a radiator or heat exchanger coreassembly from a different perspective showing the position of thestainless steel plates in relation to other elements of the radiatorcore as well as showing the location of the top and bottom header plateswhich are attached to the radiator or heat exchanger core assembly; and

FIG. 3 is a flowchart of the process steps of the system and method ofthe present invention.

DESCRIPTION OF THE EMBODIMENTS

Reference is made to FIGS. 1 and 2 for a description location of thecomponents a typical radiator or heat exchanger core assembly 10. Thestainless steel side plates 14 are attached to each side of the coreportion 12 of the radiator or heat exchanger core assembly 10.Alternatively stainless steel bracketry 25, and/or componentry formounting of the radiator or heat exchanger core assembly 10 may be usedin addition to or in place of the stainless steel side plates 14. Abracket may be a stainless steel girdle which may be used for support.The radiator or heat exchanger core 12 is made up of a plurality of finplates 18 which are mounted between coolant tubes 16 as is well known inthe art.

FIG. 2 shows the location of the top header 20 and the location of thebottom header 21 on either side of the heat exchanger core assembly 10.The actual locations and number of fin plates 18 and coolant tubes 16may vary depending on the amount of fluid cooling required.

FIG. 3 is a generalized flowchart showing the basic process stepsassociated with the use of the process of manufacture of a radiator orheat exchanger core assembly 10.

As shown in FIG. 3, the first step 101 in the disclosed process isapplying a light and even coat of a commercially available CuproBraze®paste or its equivalent ribbon or film on one side of the stainlesssteel side plates 14 and both sides of the coolant tubes 16. TheCuproBraze® paste is then dried 102 using a variety of different waysknown to persons having ordinary skill in the art. In the preferredembodiment the CuproBraze® paste is dried at approximately 120° C. for 5minutes. The coolant tubes 16, fin plates 18, and stainless steel sideplates 14 are then assembled 103 in a press with the coated sides of thestainless steel side plates 14 in physical contact with the fin plates18. This assembly is held together with a clamp which is placed in aposition to hold the stainless steel side plates 14 to the radiator orheat exchanger core 12.

After removing the radiator or heat exchanger core assembly 10 with thestainless steel side plates 14 attached thereto from the press, the topheader 20 and bottom header 21 are then pressed 104 on the ends of thecoolant tubes 16 and a coat of the CuproBraze® paste or its equivalentribbon or film is applying 105 on to the header/tube joints. Thiscombination of radiator or heat exchanger core 12 with stainless steelside plates 14 affixed thereto and the top and bottom headers 20 and 21is then placed into an oven constructed to enable use of the CuproBraze®brazing technique. Once in the oven, the clamped together parts are runthrough a heating cycle 106 as is known in the art. The heating cycleincludes an approximately a 5 minute±1 minute purge, a rapid warm-up toapproximately 1243° F.±10° F., a 60 second±30 second soak time atapproximately 1243° F.±10° F., followed by a cool down to approximatelyroom temperature to 200° F.

The radiator or heat exchanger core assembly 10 with the top and bottomheaders 20, 21 affixed thereto is then removed from the oven constructedto enable the CuproBraze® brazing technique. The clamp is removed andthe radiator or heat exchanger core assembly 10 with the top and bottomheaders 20, 21 attached is first inspected and then pressure tested forleaks.

OTHER USES FOR STAINLESS STEEL WITH A RADIATOR OR HEAT EXCHANGER CORE

In addition to the above described preferred embodiment of the systemand method of the present invention, the system and method of thepresent invention may be used to fabricate radiators or heat exchangersfor special uses. Among these special uses are the following situations:

1. In situations where heat is to be extracted from highly corrosivefluids by use of the disclosed process—a heat exchanger using theprocess of the present invention can be built with stainless steeltubes/headers/tanks while still using the high efficiency copper fins.

2. For show applications wherein a stainless steel/copper radiatorand/or transmission fluid coolers can be built using the process of thepresent invention and then polished to a high luster.

3. For extremely harsh conditions, such as off-road racing or heavyconstruction equipment wheeled or tracked, a radiator assembly can bemade using the disclosed process with stainless steeltubes/headers/tanks using the process of the present invention would beable to stand more abuse without leaking.

In all respects, it should also be understood that the drawings anddetailed description herein are to be regarded in an illustrative ratherthan in a restrictive manner, and are not intended to limit the systemand method of the present invention to the example disclosed. Rather,the system and method of the present invention includes all processeswithin the scope and spirit of the invention as claimed, as the claimsmay be amended, replaced or otherwise modified during the course ofrelated prosecution. Any current, amended, or added claims should beinterpreted to embrace all further modifications, changes,rearrangements, substitutions, alternatives, design choices, andembodiments that may be evident to those of skill in the art, whethernow known or later discovered. In any case, all substantially equivalentprocesses should be considered within the scope of the disclosedinvention and, absent express indication otherwise, all structural orfunctional equivalents are anticipated to remain within the spirit andscope of the disclosed system and method.

1) A process for attaching stainless steel side plates to thecopper/brass tubes and fins of a radiator or heat exchanger core, saidprocess comprising the steps of: i) applying a light even coat of aCuproBraze® paste or its equivalent ribbon or film to one side of saidstainless steel side plates and drying at approximately 120° C. for 5minutes; ii) applying a light even coat of a CuproBraze paste or itsequivalent ribbon or film to both sides of said copper/brass tubes ofsaid radiator or heat exchanger core and drying at approximately 120° C.for 5 minutes; iii) assembling said copper/brass tubes and fins of saidradiator or heat exchanger core in a press placing the coated sides ofsaid stainless steel side plates against the coated sides of saidradiator or heat exchanger core and compressing together; iv) placingheaders on the end of said copper/brass tubes v) applying CuproBrazepaste or its equivalent ribbon or film on the joints between saidheaders and said copper/brass tubes vi) heating in an oven according tothe following cycle: (1) a purge of about five minutes±one minute; (2) arapid warm up to about 1243° F.±10° F.; (3) an about 60 second±30 secondheat soak at about 1243° F.±10° F.; (4) a cool/down to approximatelyroom temperature to 200° F. 2) A radiator or heat exchanger coreassembly made according to the steps of claim 1.